The purpose of an air gap, in an air gap reverse osmosis system (RO) faucet or dishwasher air gap is to prevent back flow from contaminated waste water from a sewage or septic system from flowing backward into a residential dishwasher or reverse osmosis drinking water purification system, contaminating them, and further, preventing the contaminated back flow from intruding into the greater municipal or well water system. The common air gap RO faucet and dishwasher air gap all feature a waste water line from the water using system such as a residential reverse osmosis system or dishwasher, into the air gap device, through the gap which is vented to the atmosphere through an exposed opening in the air gap apparatus known as the air gap window, and then through a larger tube into which the waste water can then enter into the home's waste water sewage or septic system. It is understood that inherent with this design is that if the larger waste water system has inadequate drainage, waste water will fail to drain from the reverse osmosis system or dishwasher into the intended drain system and instead back up and discharge from the air gap window. When used in conjunction with a surface mount sink the waste water would then trickle back into the sink basin causing little or no harm. However when installed on an under mount sink, the use of both dishwasher air gap and air gap fixtures has become a household hazard. When used on an under mount sink application the waste water which has backed up through the air gap window is not channeled anywhere, and will spread across the sink counter top making a huge mess, then flows onto the floor, potentially damaging the floor, and creating a slip-and-fall hazard.